Although he enrolled in college and achieved straight As, he dropped out after a year. He saw an advertisement for a modeling agency at a place called John Roberts Powers, where he received some free training. During his training he was picked out for talent by commercial agent Bob Hoover. He was set up with an agent and acting coaches. From there he was sent out into the world of acting and discovered the Meisner acting method. He had no dream to become an actor at the time.[6]
For most of his life, Mark believed Bill Pellegrino (whom his mother divorced when he was two years old) was his biological father. As an adult, Mark ran a search on ancestry.com to learn more about his heritage. He discovered his DNA did not indicate Italian ancestry. Before the COVID-19 pandemic, he asked fans of TV show Supernatural on Twitter (now named X)[7] if they would be interested in finding his real father. Within an hour of posting, his father was found along with the knowledge of having two sisters and three brothers.[8][9] His biological father, Gerry, is of German descent.[10][11]
In 1998, he played the Blonde Treehorn Thug who stuffs The Dude's head down the toilet and drops his bowling ball, breaking the floor tile, in the cult film The Big Lebowski.
In 1999, he appeared in season 7, episode 3 of The X-Files as a disgruntled fast food joint employee. He was featured in National Treasure as the background FBI agent known as Agent Johnson.
In 2006, he played Sadik Marku, an Albanian mob boss, in two episodes of Without a Trace. The first episode was in season 4, episode 22 where he guest starred alongside Mark Sheppard who played Crowley in Supernatural. The second episode was in season 5, episode 5 where he guest starred alongside Rachel Miner who played Meg Masters also which is a role in Supernatural.
In March 2009, he was cast on the ABC series Lost for an appearance in the final 2 episodes of Season 5, to play the role of the mysterious Jacob. Although the press release for the episode refers to his character simply as man No. 1, the episode revealed that he portrayed Jacob, a mysterious character pivotal to the show's plot.
On June 26, 2009, it was also announced that he was cast in a recurring role as Lucifer in season 5 of the CW series Supernatural. He played a recurring role as Lucifer in season 7, and a main role as his character in seasons 12 and 13. He played a main role in season 14 as Nick, Lucifer's vessel, and was a special guest in season 15.
In 2011 he portrayed James Bishop, the leader of a vampire clan based in Boston, in the SyFy horror series Being Human in the first season, and reprised his role in seasons 2-4 as a recurring guest.[12]
In 2011, he and Curtis Armstrong, who played Metatron on Supernatural, guest starred alongside each other as well as their characters being enemy lawyers in season 7 of The Closer.
In 2012, he played a man that took a hit out on his wife, who also took one out on him, Daniel Drake in season 2, episode 8 of Person of Interest.
In 2015, he joined the ABC thriller series Quantico playing the recurring role of Clayton Haas.[13]
In 2018, he voiced and motion captured his first video game role as antagonist Jacob Seed in one Ubisoft's Far Cry 5.
He has stated that his favorite thing to do in the world is to teach[16] and if he was not an actor his alternate career would be to teach history.[17]
He is a follower of Objectivism, a philosophy created by Russian-American writer Ayn Rand.[19] Before that he used to be an environmentalist and a registered Democrat.[20] Two of the ways he spreads Rand's views are through two YouTube platforms. The first one is through an affiliation with the Ayn Rand Centre UK,[21] and the second is to his own account with a series he has created called: Reality Checks, which are videos of ideas based on philosophical topics of everyday life.[22]
He is a co-founder of The American Capitalist Party.[24][25] The party stands for individual rights, limited constitutional government, and laissez-faire capitalism.[26]
^"Ep. 187 An Interview with Mark Pellegrino!", Five Minutes with Robert & Amy Nasir, November 29, 2023, retrieved December 2, 2023 – via YouTube - Time Starts at 1:09:04 and Ends at 1:10:40.
^Being Human (Drama, Fantasy, Horror), Muse Entertainment Enterprises, Zodiak USA, Quebec Film and Television Tax Credit, January 17, 2011, retrieved May 7, 2022.